JP2013169130A - Load control device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more reliably switch two loads at the same zero-cross point.SOLUTION: A switching control circuit 85 of a heater control section 61 outputs a non-conduction signal to one of a first switching section 70 and a second switching section 75 while outputting a conduction signal to the other thereof at timing when a predetermined delay time period D has elapsed from a zero-cross point of an AC power source 10 detected by a zero-cross detecting section 80. Further, when the conduction signal or non-conduction signal is input, the first switching section 70 brings a first load 46 into a conductive state or a non-conductive state at the zero-cross point of the AC power source 10 immediately after the conduction signal or non-conduction signal is input. When the conduction signal or non-conduction signal is input, the second switching section 75 similarly brings a second load 47 into the conductive state or the non-conductive state at the zero-cross point of the AC power source 10 immediately after the conduction signal or non-conduction signal is input. Thus, the two first and second loads 46 and 47 can be more reliably switched at the same zero-cross point.

Description

  The present invention relates to a load control device and an image forming apparatus.

  2. Description of the Related Art Conventionally, there is known a load control device that switches between energization / non-energization for a load that is operated by an AC power source such as a heater used in an image forming apparatus. For example, in the power control device described in Patent Document 1, when the heater operation signal is turned on, when the zero cross signal from the zero cross detection circuit is turned on, the CPU turns on the heater control signal to make the triac conductive, and the triac Turn on the heater connected in series. Thus, the inrush current at the time of heater energization can be suppressed by energizing the heater at the zero cross point of the AC power supply using the zero cross detection circuit.

JP 2002-84736 A

  Here, when the zero cross detection circuit outputs a switching signal for energization / non-energization of the load when the zero cross detection circuit detects the zero cross point of the AC power supply as in Patent Document 1, the timing at which the load is actually switched may vary. . For example, the load may be switched at the same zero cross point as the zero cross point detected by the zero cross detection circuit, or may be switched at the next zero cross point. Causes of such variations include, for example, distortion of the waveform of the AC power supply, phase difference (power factor) between current and voltage, distortion of the rising or falling waveform of the switching signal, and delay until the switching signal is output. Variations are considered. When this happens, for example, the deviation between the detection timing of the zero cross detection circuit and the actual zero cross point becomes large, the time from the detection timing of the zero cross detection circuit to the output of the subsequent switching signal is not stable, Since the time from when the switching signal is output to when the load is actually switched is not stable, the switching timing varies.

  Such a phenomenon becomes a problem particularly when it is desired to simultaneously switch one of the two loads to the energized state and the other to the non-energized state. For example, if one of the loads is energized first at a certain zero cross point and the other is de-energized at the subsequent zero cross point, there will be a period in which both loads are energized, resulting in an instantaneous overcurrent state. . Similarly, when one of the loads is de-energized first and the other is energized later, there is a period during which both loads are de-energized, and the load is instantaneously unloaded. When an instantaneous overcurrent state or no-load state occurs, there are problems such as the occurrence of flickering in peripheral devices, and in the case of an overcurrent, there is a problem that damage is accumulated in the fuse and it is easy to blow.

  The present invention has been made in view of the above-described problems, and has as its main object to switch two loads more reliably at the same zero cross point.

  The present invention adopts the following means in order to achieve the main object described above.

The load control device of the present invention includes:
A load control device that is connected to a first load and a second load that are operated by energization of an AC power supply, and that switches between the energized state and the de-energized state for each of the first load and the second load. There,
When a predetermined energization signal is input, the first load is energized at the nearest zero cross point of the AC power supply after the energization signal is input, and when the predetermined deenergization signal is input, First switching means for bringing the first load into a non-energized state at a zero cross point of the AC power supply immediately after being input;
When the predetermined energization signal is input, the second load is energized at the nearest zero cross point of the AC power supply after the energization signal is input, and when the predetermined deenergization signal is input, Second switching means for bringing the second load into a non-energized state at the zero cross point of the most recent AC power supply after being input;
Zero-cross detection means for detecting a zero-cross point of the AC power supply;
The energization signal is output to one of the first switching means and the second switching means at the timing after the elapse of a predetermined delay time from the zero cross point detected by the zero cross detection means, and the non-energization signal is applied to the other. Switching control means for outputting;
It is equipped with.

  In the load control device of the present invention, an energization signal is output to one of the first switching means and the second switching means at a timing after a predetermined delay time has elapsed from the zero cross point of the AC power supply detected by the zero cross detection means. At the same time, a non-energization signal is output to the other. Then, when the energization signal or the non-energization signal is input, the first switching unit brings the first load into an energized state or a non-energized state at the zero cross point of the most recent AC power supply after the input. Also for the second switching means, when an energization signal or a deenergization signal is input, the second load is brought into an energized state or a non-energized state at the zero cross point of the most recent AC power supply after the input. In this way, the energization signal and the deenergization signal are output at the timing after the delay time has elapsed since the zero cross point of the AC power supply detected by the zero cross detection means. As a result, the timing at which the energization signal and the non-energization signal are input to the first switching unit and the second switching unit is shifted backward, so that both the first load and the second load are detected by the zero cross detection unit. It becomes difficult to switch at the same zero cross point. Here, for example, when the zero-cross detection means detects a zero-cross point, the energization signal or the non-energization signal is output immediately. For example, the timing is determined by the signal output to the first switching means and the signal output to the second switching means. Even if a slight deviation occurs, only one of the first load and the second load is switched at the same zero cross point as the zero cross point detected by the zero cross detection means, and the other is switched at the next zero cross point. Easy to get up. In the load control device of the present invention, this can be further suppressed by providing a predetermined delay time. Thereby, two loads can be more reliably switched at the same zero cross point. Moreover, the occurrence of an instantaneous overcurrent state or no-load state can be further suppressed by switching the two loads more reliably at the same zero cross point.

  In the load control apparatus of the present invention, the switching control means may be means for setting the delay time based on a time interval of zero cross points detected by the zero cross detection means. In this way, the delay time can be made variable according to the time interval of the zero cross point, that is, the period of the AC power supply. This makes it easy to set the delay time to an appropriate value.

  In the load control apparatus of the present invention, the switching control means may be means for setting a half time of the time interval of the zero cross point detected by the zero cross detection means as the delay time. Assuming that the delay time is half the time interval of the zero cross point, that is, the time of a quarter cycle of the AC power supply (phase 90 °), the timing when the energization signal and the non-energization signal are input to the first switching means and the second switching means. Near the middle of the continuous zero cross point of the AC voltage. Therefore, for example, even if there is a difference between the timing at which the signal is output to the first switching means and the timing at which the signal is output to the second switching means, it can be further suppressed that only one timing crosses the zero cross point. . Thereby, two loads can be more reliably switched at the same zero cross timing.

  In the load control device of the present invention, the delay time may be a value predetermined as a quarter cycle of the AC power supply. In this way, when the cycle of the AC power source is a known value, for example, the energization signal and the second switching unit are not supplied to the first switching unit and the second switching unit without performing the process of setting the delay time based on the time interval of the zero cross point. The timing at which the non-energization signal is input can be set near the middle of the zero cross point where the AC voltage continues. Thereby, two loads can be more reliably switched at the same zero cross timing.

  In the load control device of the present invention, the first switching means is a light-emitting diode that is turned on when the energization signal is input and turned off when the de-energization signal is input, and the light-emitting diode is turned on and the AC power supply A triac coupler comprising an auxiliary triac in which current flows through the G (gate) terminal at the time of the zero cross point and the T1 and T2 terminals are electrically connected, and the T1 and T2 terminals are connected in series to the first load. One of the T1, T2 terminals of the auxiliary triac is connected to its own G terminal, and the T1, T2 terminals of the auxiliary triac are connected to each other by conduction between the T1, T2 terminals of the auxiliary triac. The second switching means includes a light emitting diode that turns on when the energization signal is input and turns off when the deenergization signal is input, and the light emitting diode. And a triac coupler comprising an auxiliary triac in which current flows through the G (gate) terminal and conducts between the T1 and T2 terminals at the timing of the zero cross point of the AC power supply, and the T1 and T2 terminals are the second A main triac that is connected in series with a load and one of the T1 and T2 terminals of the auxiliary triac is connected to its own G terminal and the T1 and T2 terminals of the auxiliary triac are connected by conduction between the T1 and T2 terminals of the auxiliary triac. And may have. By so doing, it is possible to switch between the energized state and the non-energized state of the first load and the second load using the triac coupler and the main triac. Further, since the triac coupler is used, it is possible to insulate the circuit on the switching control means side that outputs an energization signal or a non-energization signal to the light emitting diode from the main triac or the auxiliary triac to which the AC power is applied.

  In the load control device of the present invention, the zero-cross detection means includes a full-wave rectifier circuit that rectifies a voltage from the AC power supply with the AC power supply connected to an input terminal, and a high-frequency output terminal of the full-wave rectifier circuit. You may have the photocoupler which consists of a light emitting diode and a phototransistor which the anode was connected to the electric potential side, and the cathode was connected to the low electric potential side. In this way, the light-emitting diode is turned off at the zero cross point of the AC power supply and the phototransistor is turned off. In other cases, the light-emitting diode is turned on and the phototransistor is turned on. can do. In addition, since the light emitting diode to which the rectified voltage from the AC power supply is applied and the phototransistor are insulated, the circuit connected to the phototransistor such as a switching control means using the detection result of the zero cross point is connected from the AC power supply. Can be insulated.

  In the load control device of the present invention, the first load and the second load may be any one of a halogen lamp, a heater element, and a fan. Since the halogen lamp, the heater element, and the fan all operate at a relatively large current, it is highly significant to switch the two loads more reliably at the same zero cross timing to suppress the occurrence of an overcurrent state or a no-load state.

The image forming apparatus of the present invention includes:
The load control device of the present invention according to any one of the aspects described above;
A head for discharging liquid to form an image on a medium;
A heater element that operates by energization of the AC power source and heats the medium to dry the liquid discharged onto the medium, and the load control device switches between energized and de-energized states. A first load and a second load,
It is equipped with.

  Since the image forming apparatus of the present invention includes the above-described load control apparatus of the present invention, the same effect as the above-described load control apparatus of the present invention, for example, two loads can be switched more reliably at the same zero cross point. The effect that can be obtained.

1 is a configuration diagram showing an outline of the configuration of a printer 20 according to an embodiment of the present invention. The circuit diagram of the heater control part 61. FIG. The graph when the heater control part 61 switches the 1st load 46 and a 2nd load. The graph which shows an example when delay time D = 0 and an overcurrent state arises. The graph which shows an example when delay time D = 0 and a no-load state arises.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing an outline of a configuration of a printer 20 according to an embodiment of the present invention. FIG. 1 also shows a configuration excluding the cover 42 and the heater 45. The printer 20 of this embodiment is configured as an ink jet printer, and as shown in FIG. 1, ink as a fluid is applied from a print head 24 to a print medium S (for example, recording paper) conveyed on a platen 40. The printing mechanism 21 that performs printing by discharging, and the conveyance roller 35 driven by the drive motor 33 causes the printing medium S to pass over the platen 40 from the upstream side in the conveyance direction (the back in the figure) to the downstream side in the conveyance direction (the near side in the figure). ) Includes a transport mechanism 31 for transporting the print medium S. The printer 20 includes a capping device 41 that is formed at the right end of the platen 40 in the drawing and seals the print head 24; a heater 45 that is attached to the back surface of the cover 42 that covers the printing mechanism 21 and heats the print medium S; A controller 50 that controls the entire printer 20, a power supply circuit 60 that is connected to an AC power supply 10 (for example, a commercial power supply) and supplies power to each unit of the printer 20, and a heater control unit that is connected to the AC power supply 10 and controls the heater 45. 61. The printer 20 is configured as an image forming apparatus that forms an image by printing on the printing medium S using ink that is heated and dried by a heater 45.

  The printing mechanism 21 ejects ink droplets onto the carriage 22 that reciprocates in the main scanning direction (left and right) along the guide 28 by the carriage belt 32 and the print medium S that passes over the platen 40 as the carriage motor 34 a is driven. A print head 24 that forms an image, and an ink cartridge 26 that individually stores ink of each color and supplies the ink to the print head 24. The carriage 22 includes a carriage motor 34a disposed on the right side of the mechanical frame 48, a driven roller 34b disposed on the left side of the mechanical frame 48, and a carriage belt 32 installed on the carriage motor 34a and the driven roller 34b. It moves in the main scanning direction that intersects the transport direction of the print medium S. An encoder 36 for detecting the position of the carriage 22 is disposed on the rear surface of the carriage 22, and the position of the carriage 22 can be managed using the encoder 36.

  The print head 24 is provided in the lower part of the carriage 22, and ink of each color is supplied from nozzles provided on the lower surface of the print head 24 by applying a voltage to the piezoelectric elements to deform the piezoelectric elements and pressurize the ink. Is discharged. The print head 24 may employ a method in which the ink is pressurized by bubbles generated by applying a voltage to the heating resistor to heat the ink. The ink cartridge 26 is mounted on the mechanical frame 48 side, and each color of yellow (Y), magenta (M), cyan (C) and black (K) containing a dye or pigment as a colorant in water as a solvent. Contains ink separately.

  The print head 24 is provided with a temperature sensor 38 that measures the temperature of the printing area on the platen 40. The temperature sensor 38 is configured as a non-contact pyroelectric infrared sensor that measures the temperature of an object by extracting a temperature change due to infrared rays incident from the vertical direction (directly below) as an electrical signal, and is located on the platen 40. The temperature of the print medium S can be measured. The temperature sensor 38 can measure the temperature of one or more locations including the heated print medium S as the print head 24 moves.

  The platen 40 is a member that supports the print medium S that is conveyed below the print head 24 and heated by the heater 45, and the main scanning direction of the print head 24 faces the print head 24 that moves along the guide 28. It is formed along.

  The heater 45 is located above the carriage 22 and the platen 40, and includes a first load 46 disposed on the downstream side in the transport direction and a second load 47 disposed on the upstream side in the transport direction. The first load 46 and the second load 47 are heater elements that generate heat by a resistance heating method, whereby the heater 45 heats the print medium S passing over the platen 40 and dries the ink discharged to the print medium S. It is possible to make it. The heater 45 has a longer main scanning direction than the printing medium S, and can heat the entire printing medium S substantially uniformly in the main scanning direction. The first load 46 and the second load 47 of the heater 45 are connected in parallel and operate (heat generation) when the AC power supply 10 is energized. In the present embodiment, the first load 46 has a resistance value R, and the second load 47 has a resistance value 2R. Therefore, the heater when the first load 46 is in the energized state and the second load 47 is in the non-energized state is compared with the heater when the first load 46 is in the non-energized state and the second load 47 is in the energized state. The output (heat generation amount) of 45 is doubled.

  The power supply circuit 60 is a circuit that is connected to the AC power supply 10 and supplies the power supplied from the AC power supply 10 to each unit of the printer 20. The power supply circuit 60 converts AC power supplied from the AC power supply 10 into DC power by an AC-DC conversion circuit (not shown), and the printer 20 such as the printing mechanism 21, the transport mechanism 31, the controller 50, and the heater control unit 61. Supply to each part. The power supply circuit 60 supplies a DC voltage such as DC 20 V or DC 5 V in accordance with the operating voltage of the supply destination. The power supply circuit 60 functions as a DC power supply Vcc that supplies DC5V to the heater control unit 61. Note that the DC power supply Vcc may be a voltage of about several volts such as DC 3.3V, and is not limited to DC 5V.

  The heater control unit 61 is connected to the AC power supply 10 and the heater 45, and switches the first load 46 and the second load 47 of the heater 45 to be in an energized state or in a non-energized state. FIG. 2 is a circuit diagram of the heater control unit 61. As shown in the figure, the heater control unit 61 is connected to a pair of input terminals 62a and 62b connected to the AC power source 10, and an electric circuit between the input terminal 62a and the first switching unit 70 and the heater 45, and is not less than a predetermined value. A fuse 65 that blows when an overcurrent flows, a first switching unit 70 that switches the first load 46 between an energized state and a non-energized state, and a second load 47 that is energized or de-energized. Based on the second switching unit 75 that switches between the zero-crossing point, the zero-crossing detecting unit 80 that detects the zero-crossing point of the AC power supply 10 input via the input terminals 62a and 62b, and the zero-crossing point detected by the zero-crossing detecting unit 80. And a switching control circuit 85 that outputs energization signals and non-energization signals to the first switching unit 70 and the second switching unit 75.

  The first switching unit 70 is a circuit that switches between an energized state and a non-energized state of the first load 46, and includes a triac coupler 71, a main triac TM1, a resistor R1, and a transistor TR1. The triac coupler 71 is connected to a light emitting diode LED1 whose anode is connected to the DC power source Vcc and the cathode is connected to the collector of the transistor TR1 via a pull-up resistor Rv1, and a zero cross circuit ZC1 for detecting the zero cross point of the AC power source 10. And an auxiliary triac TS1 configured as a known triac with a zero-cross circuit. In the main triac TM1, the T2 terminal of the auxiliary triac TS1 is connected to the G (gate) terminal, and the T1 terminal of the auxiliary triac TS1 is connected to the T2 terminal of the main triac TM1 via the resistor R1. The T1 and T2 terminals of the main triac TM1 are connected in series with the first load 46. The transistor TR1 has a base connected to the Vout1 terminal of the switching control circuit 85, an emitter grounded, and a collector connected to the DC power supply Vcc via the light emitting diode LED1 and the pull-up resistor Rv1.

  In the first switching unit 70, when a high voltage is input from the Vout1 terminal of the switching control circuit 85 to the base of the transistor TR1 as a predetermined energization signal, the transistor TR1 is turned on, and a current flows through the light emitting diode LED1 to cause the light emitting diode. LED1 lights up. When the light emitting diode LED1 is turned on and the zero cross circuit ZC1 detects the zero cross point of the AC power supply 10, a current flows through the G terminal of the auxiliary triac TS1 at that timing, and T1 and T2 of the auxiliary triac TS1 are conducted. Then, conduction between the T1 and T2 terminals of the auxiliary triac TS1 causes a current to flow through the G terminal of the main triac TM1, and conduction between the T1 and T2 terminals of the main triac TM1 causes the first load 46 to be energized. As described above, when the energization signal is input, the first switching unit 70 turns on the main triac TM1 at the zero cross point of the most recent AC power supply 10 after the energization signal is input, and puts the first load 46 in the energized state. To do. On the other hand, when a low voltage is input to the base of the transistor TR1 from the Vout1 terminal of the switching control circuit 85 as a predetermined de-energization signal, the transistor TR1 is turned off and the light emitting diode LED1 is turned off without flowing current. Then, the auxiliary triac TS1 and the main triac TM1 are turned off at the zero cross point of the AC power supply 10 due to the triac latching action, and the first load 46 is in a non-energized state. As described above, when the de-energization signal is input, the first switching unit 70 turns off the main triac TM1 at the zero cross point of the most recent AC power supply 10 after the de-energization signal is input, and de-energizes the first load 46. Turn on the power. Note that the resistance value of the pull-up resistor Rv1 is set to an appropriate value (for example, 1 kΩ) so that the collector current that flows when the transistor TR1 is turned on is limited to a circuit allowable value or less.

  The second switching unit 75 is a circuit that switches between the energized state and the non-energized state of the second load 47, and instead of the Vout 1 terminal of the first load 46 and the switching control circuit 85, the second load 47 and the switching control circuit 85. The configuration is the same as that of the first switching unit 70 except that it is connected to the Vout2 terminal. That is, the second switching unit 75 includes a triac coupler 76, a main triac TM2, a resistor R2, and a transistor TR2. The triac coupler 76 is connected to a light emitting diode LED2 whose anode is connected to the DC power source Vcc and the cathode is connected to the collector of the transistor TR2 via the pull-up resistor Rv2, and a zero cross circuit ZC2 for detecting the zero cross point of the AC power source 10. And an auxiliary triac TS2 configured as a known triac with a zero-cross circuit. In the main triac TM2, the T2 terminal of the auxiliary triac TS2 is connected to the G (gate) terminal, and the T1 terminal of the auxiliary triac TS2 is connected to its own T2 terminal via the resistor R2. The T1 and T2 terminals of the main triac TM2 are connected in series with the second load 47. The transistor TR2 has a base connected to the Vout2 terminal of the switching control circuit 85, an emitter grounded, and a collector connected to the DC power source Vcc via the light emitting diode LED2 and the pull-up resistor Rv2.

  In the second switching unit 75, when a high voltage is input from the Vout2 terminal of the switching control circuit 85 to the base of the transistor TR2 as a predetermined energization signal, the transistor TR2 is turned on and a current flows through the light emitting diode LED2 so that the light emitting diode LED2 lights up. Subsequently, when the light-emitting diode LED2 is turned on and the zero-crossing circuit ZC2 detects the zero-crossing point of the AC power supply 10, current flows through the G terminal of the auxiliary triac TS2 at that timing, and T1 and T2 of the auxiliary triac TS2 become conductive. . Then, due to the conduction between the T1 and T2 terminals of the auxiliary triac TS2, a current flows through the G terminal of the main triac TM2, the conduction between the T1 and T2 terminals of the main triac TM2 is established, and the second load 47 is energized. As described above, when the energization signal is input, the second switching unit 75 turns on the main triac TM2 at the zero cross point of the AC power supply 10 immediately after the energization signal is input, and puts the second load 47 in the energized state. To do. On the other hand, when a low voltage is input from the Vout2 terminal of the switching control circuit 85 to the base of the transistor TR2 as a predetermined non-energization signal, the transistor TR2 is turned off and the light emitting diode LED2 is turned off without flowing current. Then, the auxiliary triac TS2 and the main triac TM2 are turned off at the zero cross point of the AC power supply 10 by the latching action of the triac, and the second load 47 is in a non-energized state. As described above, when the de-energization signal is input, the second switching unit 75 turns off the main triac TM2 at the zero cross point of the most recent AC power supply 10 after the de-energization signal is input, and de-energizes the second load 47. Turn on the power. Note that the resistance value of the pull-up resistor Rv2 is set to an appropriate value (for example, 1 kΩ) so that the collector current that flows when the transistor TR2 is turned on is limited to a circuit allowable value or less.

  The zero-cross detector 80 is a circuit that detects a zero-cross point of the AC power supply 10 and includes a full-wave rectifier circuit 81, a resistor R3, and a photocoupler 82. The full-wave rectifier circuit 81 is configured as a diode bridge, and its own input terminal is connected between the input terminals 62a and 62b, and rectifies the voltage from the AC power supply 10. The photocoupler 82 includes a light emitting diode LED3 and a phototransistor PT. The light emitting diode LED3 has an anode connected to the high potential side of the output terminal of the full wave rectifier circuit 81 via the resistor R3 and a cathode connected to the low potential side of the output terminal of the full wave rectifier circuit 81. . The phototransistor PT has a collector connected to a DC power source Vcc via a pull-up resistor Rv3 and is connected to a Vin terminal (to be described later) of the switching control circuit 85, and an emitter is grounded. In the zero-cross detector 80, the voltage of the AC power supply 10 rectified by the full-wave rectifier circuit 81 is applied to the light emitting diode LED3. Therefore, near the zero cross point of the AC power supply 10, the light emitting diode LED3 is turned off, the phototransistor PT is turned off, and the voltage at the Vin terminal becomes high. On the other hand, in other cases, the light emitting diode LED3 is turned on and the phototransistor PT is turned on, so that a collector current flows through the phototransistor PT, and the voltage at the Vin terminal becomes low. In this way, the zero cross detection unit 80 detects the zero cross point of the AC power supply 10 by turning on and off the phototransistor PT.

  The switching control circuit 85 is configured as a microcomputer, and has a Vcc terminal to which a DC power supply Vcc is input, a Vs terminal to which a switching signal of the heater 45 is input from the controller 50, and a DC via a pull-up resistor Rv3. A Vin terminal connected to the power supply Vcc and connected to the collector of the phototransistor PT, a Vout1 terminal connected to the base of the transistor TR1 of the first switching unit 70, and a base of the transistor TR2 of the second switching unit 75 A Vout2 terminal and a GND terminal grounded to the ground. The Vcc terminal and the GND terminal are input terminals for the control voltage of the switching control circuit 85, and the switching control circuit 85 is operated by the voltage from the DC power supply Vcc applied between the Vcc terminal and the GND terminal. The Vin terminal has the same potential as the ground, that is, low when the phototransistor PT of the zero-cross detection unit 80 is on, and has the same potential, that is, the high level, as that of the DC power supply Vcc when the phototransistor PT is off.

  When the switching signal from the controller 50 is input, that is, when the Vs terminal becomes high, the switching control circuit 85 detects the most recent zero cross point after that when the potential of the Vin terminal becomes high. A high voltage as an energization signal is applied to one of the first switching unit 70 and the second switching unit 75, that is, one of the Vout1 terminal and the Vout2 terminal at a timing after a predetermined delay time D has elapsed from the zero cross point. The other side outputs a low voltage as a non-energization signal. Here, the switching control circuit 85 always keeps one of the first load 46 and the second load 47 in an energized state and the other in a non-energized state. An energization signal and a non-energization signal are output so that the load 46 and the second load 47 are alternately energized. For example, when the switching signal is input from the controller 50 when the first load 46 is in the energized state and the second load 47 is in the non-energized state, the switching control circuit 85 changes the voltage output from the Vout1 terminal from high to low. In addition, a non-energization signal is output to the first switching unit 70, and a voltage output from the Vout2 terminal is changed from low to high to output an energization signal to the second switching unit 75. In the following description, the energization signal and the non-energization signal may be collectively referred to as a control signal. Further, the switching control circuit 85 measures the rising time interval T when the potential of the Vin terminal becomes high as the time interval of the zero cross point of the AC power supply 10 detected by the zero cross detecting unit 80, and this time interval T Is set as the delay time D. Note that the switching control circuit 85 updates the value of the delay time D by measuring the time interval T every time the potential of the Vin terminal becomes high.

  The controller 50 is configured as a microprocessor centered on the CPU 52, a RAM 54 that temporarily stores data and saves data, a flash memory 55 that stores various processing programs and can rewrite data, It has. The controller 50 is connected to an interface (I / F) (not shown) for exchanging information with an external device such as a personal computer, an input / output port (not shown) for inputting / outputting data. A position signal from the encoder 36, a signal from the temperature sensor 38, and the like are input to the controller 50 via an input port. Further, the controller 50 outputs a drive signal to the print head 24, a drive signal to the drive motor 33 and the carriage motor 34a, a switch signal to the Vs terminal of the switch control circuit 85, and the like via the output port. .

  When the printer 20 configured as described above is instructed to print an image on the recording paper S by a user via a personal computer connected to the printer 20, for example, the controller 50 inputs image data to be printed from the personal computer, This is stored in the print buffer area of the RAM 74 and a print processing routine for forming an image based on the image data on the recording paper S is executed. In the print processing routine, the controller 50 controls the drive motor 33 to convey the print medium S, and controls the carriage motor 34a to eject the ink from the nozzles of the print head 24 while moving the carriage 22. Of these, the process of printing for one pass is repeated to form an image on the print medium S. At this time, the controller 50 outputs a switching signal to the switching control circuit 85 of the heater control unit 61 so that the printing medium S is heated at a constant temperature based on the temperature measured by the temperature sensor 38. For example, when the temperature of the print medium S measured by the temperature sensor 38 exceeds a predetermined threshold value, the first load 46 is deenergized and the second load 47 is energized so that the amount of heat generated by the heater 45 is reduced. A switching signal is output to the switching control circuit 85. When the temperature of the print medium S is lower than the predetermined threshold, the switching control circuit 85 is switched to increase the heat generation amount of the heater 45 by setting the first load 46 in the energized state and the second load 47 in the non-energized state. Is output.

  The operation of the heater control unit 61 when the controller 50 outputs the switching signal and switches between energization / non-energization of the first load 46 and the second load 47 will be described. FIG. 3 shows the potential of the Vs terminal, the voltage V of the AC power supply 10, and the voltage of the Vin terminal when the heater control unit 61 switches between energization / non-energization of the first load 46 and the second load 47 by the switching signal from the controller 50. 6 is a graph showing the relationship among the potential, the potential of the Vout terminal, the current I1 of the first load 46, the potential of the Vout2 terminal, the current I2 of the second load 47, and the total load current (I1 + I2) of the heater 45. As shown in the figure, when the potential of the Vout1 terminal is low and the potential of the Vout2 terminal is high, that is, when the first load 46 is in the non-energized state (I1 = 0) and the second load 47 is in the energized state, the time t1 , The switching signal is inputted from the controller 50 and the potential of the Vs terminal becomes high. In this case, first, the switching control circuit 85 of the heater control unit 61 waits until the voltage of the AC power supply 10 reaches the zero cross point, that is, until the potential of the Vin terminal becomes high. When the voltage of the AC power supply 10 becomes the zero cross point and the phototransistor PT of the zero cross detection unit 80 is turned on and the potential at the Vin terminal becomes high at time t2, the delay time D, that is, the potential at the Vin terminal becomes high from time t2. At time t3 after a half of the rising time interval T has elapsed, an energization signal is output to the first load 46 and a non-energization signal is output to the second load 47. That is, at time t3, the potential of the Vout1 terminal is changed from low to high, and the potential of the Vout2 terminal is changed from high to low. By outputting the energization signal and the non-energization signal after delaying by the delay time D = T / 2 as described above, the time t3 at which the energization signal and the non-energization signal are output is the voltage of the AC power supply 10 as can be seen from the figure. Near the peak value, that is, near the middle of two consecutive zero cross points. Then, when the Vout1 terminal becomes high at time t3, the first switch 46 becomes energized at time t5, which is the latest zero cross point after time t3, and the current I1 flows. On the other hand, it is assumed that the potential of the Vout2 terminal should change from high to low at time t3, but actually changes from high to low at time t4, which is a time α later than time t3. In such a case, the timing between the output of the energization signal to the first load 46 and the output of the non-energization signal to the second load 47 is shifted by time α. However, since the time t3 is near the middle of the zero cross point as shown in the figure, even if the time α is shifted, the time t4 does not exceed the time t5, so that the second switching unit 75 has the latest zero cross point after the time t4. At time t5, the second load 47 is turned off. For this reason, even if the output timing of the energization signal and the output timing of the non-energization signal are shifted, the zero cross point at which the first load 46 is energized and the zero cross point at which the second load 47 is de-energized are the same. Therefore, it does not enter an overcurrent state or no-load state.

  Thus, in the heater control unit 61, the energization signal and the de-energization signal are sent at a timing after the delay time D = T / 2 has elapsed from the zero cross point (time t2) of the AC power supply detected by the zero cross detection unit 80. By outputting, even if the timing between the two is shifted, the first load 46 and the second load 47 are prevented from switching at different zero cross points. Note that FIG. 3 illustrates the case where the first load 46 is energized and the second load 47 is de-energized, but the same applies to the case where the first load 46 is de-energized and the second load 47 is energized. It is. 3 shows a case where the output timing (time t4) of the control signal to the second load 47 is delayed compared to the output timing (time t3) of the control signal to the first load 46. Similarly, when the output timing of the control signal to the load 46 is delayed or when the output timing to at least one of the first load 46 and the second load 47 is advanced before the delay time D elapses, the first It is possible to prevent the load 46 and the second load 47 from switching at different zero cross points. Such deviations in the output timing of the control signal include, for example, distortion of the waveform of the AC power supply 10, phase difference (power factor) between current and voltage, distortion of the rising or falling waveform of the switching signal, and output of the control signal. This is caused by a variation in delay in the switching control circuit 85 until it is done. For example, when distortion occurs in the rising or falling waveform of the control signal, even if the output timing of the control signal to the first load 46 and the second load 47 is the same, the first switching unit 70 and the second switching unit 70 The operation timing with the switching unit 75 may be shifted. Even in such a case, as in the case described with reference to FIG. 3, the switching control circuit 85 performs the energization signal or de-energization at the timing after the delay time D has elapsed from the zero cross point of the AC power supply detected by the zero cross detection unit 80. By outputting a signal, it is possible to suppress the first load 46 and the second load 47 from being switched at different zero cross points.

  Here, the operation of the heater control unit 61 when the delay time D = 0 is described for comparison. FIG. 4 is a graph showing an example when the delay time D = 0 and an overcurrent state occurs. FIG. 5 is a graph showing an example when the delay time D = 0 and a no-load state occurs. 4 and 5 are the same as those in FIG. 3 until the time t2, and thus description thereof is omitted. As shown in FIG. 4, when the potential at the Vin terminal becomes high at time t2, if the delay time D = 0, the switching control circuit 85 immediately sets the potential at the Vout1 terminal to high and sets the potential at the Vout2 terminal to high. Go low. At this time, if the Vout1 terminal becomes high at time t2 as shown in the figure, the first load 46 becomes energized at time t6 which is the latest zero cross point after time t2 by the first switching unit 70, and the current I1 flows. . That is, the first load 46 is energized at the same zero cross point as the zero cross point detected by the zero cross detector 80. On the other hand, it is assumed that the voltage at the Vout2 terminal actually changes from high to low at time t7 after time t2. In this case, since the time t7 is later than the time t6, the first switching unit 70 causes the second load 47 to be in a non-energized state at time t8 which is the latest zero cross point after time t7. As a result, the zero cross point at which the first load 46 is energized is different from the zero cross point at which the second load 47 is de-energized, and the first load 46 and the second load 47 are changed between times t6 and t8. Both are energized to enter an overcurrent state. Similarly, in FIG. 5, the Vout2 terminal becomes low at time t2 and becomes non-energized at time t6, which is the same zero cross point as the zero cross point detected by the zero cross detection unit 80, but the Vout1 terminal is later than time t6. Becomes high at time t9, and the first load 46 is energized by the first switching unit 70 at time t10, which is the latest zero cross point after time t9. As a result, the zero cross point at which the first load 46 is energized is different from the zero cross point at which the second load 47 is de-energized, and the first load 46 and the second load 47 are changed between times t6 and t10. Both become a non-energized state and become a no-load state. As described above, when the delay time D = 0, an energization signal and a non-energization signal are output in the vicinity of the zero cross point detected by the zero cross detection unit 80, and therefore the first load 46 and the second load 47 even with a slight timing shift. The zero-crossing point at which the is switched tends to be different, and an overcurrent state and a no-current state are likely to occur.

  Here, the correspondence between the components of the present embodiment and the components of the present invention will be clarified. The heater control unit 61 of the present embodiment corresponds to the load control device of the present invention, the first switching unit 70 corresponds to the first switching unit, the second switching unit 75 corresponds to the second switching unit, and the zero cross detection unit 80 corresponds to the zero cross detection means, the switching control circuit 85 corresponds to the switching control means, the first load 46 corresponds to the first load, the second load 47 corresponds to the second load, and the print head 24 corresponds to the head. It corresponds to.

  According to the printer 20 of the present embodiment described above, the switching control circuit 85 of the heater control unit 61 is at a timing after a predetermined delay time D has elapsed from the zero cross point of the AC power supply 10 detected by the zero cross detection unit 80. An energization signal is output to one of the first switching unit 70 and the second switching unit 75 and a non-energization signal is output to the other. When the energization signal or the non-energization signal is input, the first switching unit 70 sets the first load 46 to the energized state or the non-energized state at the zero cross point of the most recent AC power supply 10 after the input. Also when the energization signal or the non-energization signal is input to the second switching unit 75, the second load 47 is brought into the energized state or the non-energized state at the zero cross point of the most recent AC power supply 10 after the input. By doing so, the two loads can be more reliably switched at the same zero cross point. Moreover, the occurrence of an instantaneous overcurrent state or no-load state can be further suppressed by switching the two loads more reliably at the same zero cross point.

  Further, since the switching control circuit 85 sets the delay time T based on the time interval T of the zero cross point detected by the zero cross detection unit 80, the switching control circuit 85 sets the delay time according to the time interval of the zero cross point, that is, the period of the AC power supply 10. It can be variable. This makes it easy to set the delay time to an appropriate value. The switching control circuit 85 sets the half time of the time interval T of the zero cross points detected by the zero cross detection unit 80 as the delay time D, so that the first switching unit 70 and the second switching unit 75 are supplied with energization signals and The timing at which the non-energization signal is input is near the middle of the zero cross point where the AC voltage is continuous. Thereby, two loads can be more reliably switched at the same zero cross timing.

  Furthermore, the energized state and the de-energized state of the first load 47 and the second load 47 can be switched using the triac couplers 71 and 76 and the main triacs TM1 and TM2. Further, since the triac couplers 71 and 76 are used, a circuit on the switching control circuit 85 side that outputs energization signals and non-energization signals to the light emitting diodes LED1 and LED2, and main triacs TM1 and TM2 to which the AC power supply 10 is applied, and auxiliary triacs. TS1 and TS2 can be insulated.

  Furthermore, since the zero-cross detector 80 includes the full-wave rectifier circuit 81 and the photocoupler 82, the zero-cross point can be detected by turning on and off the phototransistor PT of the photocoupler 82. Further, since the light-emitting diode LED3 to which the rectified voltage from the AC power supply 10 is applied and the phototransistor PT are insulated, the phototransistor PT is connected to the phototransistor PT such as the switching control circuit 85 using the detection result of the zero cross point. The circuit can be isolated from the AC power supply 10.

  In addition, since the heater control unit 61 switches between the first load 46 and the second load 47 that are heater elements that operate with a relatively large current, the two loads are more reliably switched at the same zero cross timing, and an overcurrent state or no load is detected. The significance of suppressing the occurrence of a load state is high.

  It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

  For example, in the above-described embodiment, the delay time D = T / 2 is set, but the present invention is not limited to this. For example, the delay time D may be determined as another value based on the time interval T, such as T / 3. Alternatively, the delay time D may be a predetermined value that is not based on the measured time interval T. For example, when the period of the AC power supply 10 is known, the delay time D may be determined in advance as a quarter period of the AC power supply 10. In this way, the timing at which the energization signal and the non-energization signal are input to the first switching unit 70 and the second switching unit 75 is changed to AC without performing the process of setting the delay time D based on the time interval T of the zero cross point. It can be near the middle of the zero cross point where the voltage continues.

  In the embodiment described above, the switching control circuit 85 is a microcomputer, but a circuit having the same function may be configured using a power element (power semiconductor element) or the like. The power element is more likely to cause an unstable delay or voltage distortion than a microcomputer, and the switching timing between the first load 46 and the second load 47 is thereby different. Since it is easy to shift, the significance of applying the present invention is high.

  In the above-described embodiment, the zero-cross detection unit 80 is configured by the full-wave rectifier circuit 81 and the photocoupler 82, but is not limited thereto as long as it detects the zero-cross of the AC power supply 10. For example, a circuit that detects a zero cross of the AC power supply 10 using a comparator with the ground as a reference voltage may be used.

  In the above-described embodiment, the resistance values of the first load 46 and the second load 47 are different from each other. Further, although switching between energization / non-energization of the first load 46 and the second load 47 is performed so that the temperature of the print medium S becomes constant, the present invention is not limited to this. For example, it is assumed that the second load 47 generates heat for a predetermined period from the start of printing of the printer 20 and heats the back side in the transport direction of the print medium S, and the print medium S moves forward in the transport direction as printing progresses. Heating is performed by switching between the first load 46 and the second load 47 such that the first load 46 generates heat and the front side in the transport direction of the print medium S is heated after a predetermined period of time for movement. The area may be changed.

  In the embodiment described above, the switching control circuit 85 outputs an energization signal and a non-energization signal so that the first load 46 and the second load 47 are alternately energized each time a switching signal is input from the controller 50. However, the present invention is not limited to this, and the switching control circuit may be any circuit that performs switching between the energized state and the non-energized state for each of the first load and the second load. For example, on the basis of a signal from the controller 50, the switching control circuit 85 sets the first state in which both the first load 46 and the second load 47 are in a non-energized state, and sets the first load 46 in a conductive state. The second state in which the load 47 is deenergized, the third state in which the first load 46 is deenergized and the second load 47 is energized, and both the first load 46 and the second load 47 are energized. An energization signal or a non-energization signal may be output from the Vout1 terminal and the Vout2 terminal so as to switch the first load 46 and the second load 47 to any one of the fourth states. Even in this case, when switching from the second state to the third state or switching from the third state to the second state, the first load 46 and the second load 47 are more reliably connected as in the present embodiment. The effect of switching at the same zero cross point is obtained.

  In the above-described embodiment, the heater control unit 61 heats the print medium S in the printer 20 to dry the ink discharged to the print medium S. The energization / non-energization of the first load 46 and the second load 47 of the heater 45 is performed. However, any heater may be controlled, such as a heater used for other uses of the printer 20 or a heater used in equipment other than the printer 20.

  In the above-described embodiment, the heater control unit 61 switches the first load 46 and the second load 47 as heater elements. However, any load switching may be performed. For example, the first load 46 and the second load 47 may be loads such as a halogen lamp and a fan.

10 AC power supply, 20 printer, 21 printing mechanism, 22 carriage, 24 print head, 26 ink cartridge, 28 guide, 31 transport mechanism, 32 carriage belt, 33 drive motor, 34a carriage motor, 34b driven roller, 35 transport roller, 36 Encoder, 38 Temperature sensor, 40 Platen, 41 Capping device, 42 Cover, 45 Heater, 46 First load, 47 Second load, 48 Mechanical frame, 50 Controller, 52 CPU, 54 RAM, 55 Flash memory, 60 Power supply circuit, 61 heater control unit, 62a, 62b input terminal, 65 fuse, 70 first switching unit, 71 triac coupler, 75 second switching unit, 76 triac coupler, 80 zero cross detection unit, 81 full wave rectifier circuit, 82 photocoupler, 85 switching control circuit, LED1-LED3 light emitting diode, PT phototransistor, R1, R2, R3 resistor, Rv1, Rv2, Rv3 pull-up resistor, S printing medium, TM1, TM2 main triac , TS1, TS3 Auxiliary triac.

Claims (8)

A load control device that is connected to a first load and a second load that are operated by energization of an AC power supply, and that switches between the energized state and the de-energized state for each of the first load and the second load. There,
When a predetermined energization signal is input, the first load is energized at the nearest zero cross point of the AC power supply after the energization signal is input, and when the predetermined deenergization signal is input, First switching means for bringing the first load into a non-energized state at a zero cross point of the AC power supply immediately after being input;
When the predetermined energization signal is input, the second load is energized at the nearest zero cross point of the AC power supply after the energization signal is input, and when the predetermined deenergization signal is input, Second switching means for bringing the second load into a non-energized state at the zero cross point of the most recent AC power supply after being input;
Zero-cross detection means for detecting a zero-cross point of the AC power supply;
The energization signal is output to one of the first switching means and the second switching means at the timing after the elapse of a predetermined delay time from the zero cross point detected by the zero cross detection means, and the non-energization signal is applied to the other. Switching control means for outputting;
A load control device. The switching control means is means for setting the delay time based on the time interval of the zero cross point detected by the zero cross detection means.
The load control device according to claim 1. The switching control means is means for setting a half time of the time interval of the zero cross point detected by the zero cross detection means as the delay time.
The load control device according to claim 1 or 2. The delay time is a value predetermined as a quarter cycle of the AC power supply.
The load control device according to claim 1. The first switching means turns on when the energization signal is input and turns off when the non-energization signal is input, and when the light emitting diode is on and the timing of the zero cross point of the AC power supply A triac coupler comprising an auxiliary triac in which current flows through the (gate) terminal and the T1 and T2 terminals are electrically connected, and the T1 and T2 terminals are connected in series to the first load and the T1 and T2 terminals of the auxiliary triac One of the main triacs is connected to the G terminal of the auxiliary triac, and the T1 and T2 terminals of the auxiliary triac are conducted by conduction between the T1 and T2 terminals of the auxiliary triac.
The second switching means is a light-emitting diode that is turned on when the energization signal is input and is turned off when the de-energization signal is input, and when the light-emitting diode is turned on and at the timing of the zero cross point of the AC power supply. A triac coupler comprising an auxiliary triac in which current flows through the (gate) terminal and the T1 and T2 terminals are electrically connected, and the T1 and T2 terminals are connected in series to the second load and the T1 and T2 terminals of the auxiliary triac One of the main triacs is connected to its own G terminal, and the T1 and T2 terminals of the auxiliary triac are electrically connected by conduction between the T1 and T2 terminals of the auxiliary triac.
The load control apparatus of any one of Claims 1-4. The zero-cross detection means includes a full-wave rectifier circuit that rectifies the voltage from the AC power supply with the AC power supply connected to an input terminal, and an anode connected to the high potential side of the output terminal of the full-wave rectifier circuit. And a photocoupler comprising a light-emitting diode having a cathode connected to the low potential side and a phototransistor,
The load control device according to any one of claims 1 to 5. The first load and the second load are any one of a halogen lamp, a heater element, and a fan.
The load control device according to any one of claims 1 to 6. The load control device according to any one of claims 1 to 7,
A head for discharging liquid to form an image on a medium;
A heater element that operates by energization of the AC power source and heats the medium to dry the liquid discharged onto the medium, and the load control device switches between energized and de-energized states. A first load and a second load,
An image forming apparatus.

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